Specifications for Mix Seal Surfacing (MSS) Close-Graded Premix Surfacing (CGPS)

IRC SP 78 - Introduction: Key Formulas, Tables & Specifications

1. Weather & Seasonal Limitations (Clause 4.1)

• Mix seal surfacing must NOT be laid during:
  • Rainy weather
  • Damp subgrade/base
  • Atmospheric temperature ≤ 10 ℃ (in shade)

2. Viscosity Graded (VG) Bitumen & Applications (Table 1)

3. Bitumen Selection Based on Climate (Tables 2A & 2B)

4. Aggregate Grading for Mix Seal Surfacing (Table 3)

IRC SP 78 - Scope: Key Specifications & Tables

1. Weather & Seasonal Limitations (Clause 4.1)

• Mix seal surfacing must not be laid during:
  • Rainy weather
  • Damp subgrade or base
  • Atmospheric temperature ≤ 10℃ (in shade)

2. Bitumen Selection (Tables 1, 2A & 2B)

Climatic Selection for VG Bitumen (Table 2A):

Modified Bitumen Grades (Table 2B):

3. Aggregate Grading for Mix Seal Surfacing (Table 3)

IRC SP 78: Key Material Specifications & Tables

1. Bitumen Types & Applications (Table 1)

2. Bitumen Selection by Climate (Table 2A & 2B)

Modified Bitumen Grades vary similarly with temperature (PMB/NRMB/CRMB types).

3. Aggregate Grading for Mix Seal Surfacing (Table 3)

4. Physical Requirements of Aggregates

• Aggregate Impact Value: As per contract (either this or LA Abrasion)
• Los Angeles Abrasion: Max 40%
• Soundness: Max 12% loss (Na2SO4), Max 18% loss (MgSO4)
• Flakiness Index: Max 25%
• Adhesion (retained coating): Min 95%
• Water Absorption: Max 1%

5. Tack Coat Application Rates (Table 4)

| Surface Type | Emulsion (kg/m²) | Bitumen VG-10 (kg/m²)

IRC SP 78: Construction Methods - Key Formulas, Tables & Specifications

1. Proportioning of Materials (Clause 3.3)

• Use viscosity-graded (VG) bitumen according to climate and stress conditions.
• Aggregate grading must conform to Table 3 for Mix Seal Surfacing.

2. Weather & Seasonal Limitations (Clause 4.1)

• Do not lay mix seal surfacing during:
  • Rainy weather
  • Damp subgrade/base
  • Atmospheric temperature ≤ 10°C (shade)

3. Bitumen Selection (Table 1 & 2A/2B)

Selection based on temperature:

4. Aggregate Grading for Mix Seal Surfacing (Table 3)

5. Tack Coat Application Rates (Table 4)

Weather & Seasonal Limitations (IRC SP 78 - Clause 4.1)

• Mix seal surfacing must NOT be laid:
  • During rainy weather
  • When subgrade/base is damp
  • When atmospheric temperature in shade ≤ 10°C

Key Tables & Specifications

1. Viscosity Graded (VG) Bitumen & Applications

2. Bitumen Selection Based on Climate

3. Mixing, Laying & Rolling Temperatures

Rolling must finish before mat cools below rolling temp.

Preparation of Course for Mix Seal Surfacing (IRC SP 78 - Clause 4.4):

• The underlying course must be reshaped and conditioned to a uniform grade and profile.
• All depressions and potholes should be filled and compacted before surfacing.
• The surface must be cleaned thoroughly, free from cow dung, dust, and foreign material.
• For granular courses, a prime coat must be applied before laying the mix seal surfacing.

Key Tables & Specifications:

1. Aggregate Grading for Mix Seal Surfacing (Table 3):

2. Rate of Application of Tack Coat (Table 4):

3. Weather Limitations (Clause 4.1):

• Do not lay mix seal surfacing during rainy weather or when the subgrade/base is damp.
• Atmospheric temperature in shade should be above 10°C.

Summary Flow for Preparation:

flowchart TD
    A[Existing Course] --> B[Reshape & Condition to Uniform Grade]
    B --> C[Fill & Compact Depressions/Potholes]
    C --> D[Thoroughly Sweep Clean Surface]
    D --> E{Is Course Granular?}
    E -- Yes --> F[Apply Prime Coat]

IRC SP 78: Arrangement for Traffic - Key Points

• Clause 4.3: Traffic movement must be arranged per IRC:SP:55 to ensure smooth construction without traffic interference.

• Clause 4.11: Road opening to traffic is allowed once the mix cools to ambient temperature. Initial speed restrictions are recommended to avoid mix displacement.

• Weather Limitation (Clause 4.1): Mix seal surfacing must not be laid during rain, damp subgrade/base, or when shade temperature ≤ 10°C.

Relevant Tables Summary

Practical Notes for Traffic Arrangement

• Traffic control plans should minimize disruption during construction.
• Speed restrictions after opening prevent surface damage.
• Weather conditions must be monitored to avoid poor laying conditions.

flowchart LR
    A[Construction Start] --> B[Arrange Traffic per IRC:SP:55]
    B --> C[Lay Mix Seal Surfacing]
    C -->|Mix cools to ambient temp| D[Open Road to Traffic]
    D --> E{Initial Speed Restriction?}
    E -->|Yes| F[Impose Speed Limits]
    E -->|No| G[Normal Traffic Flow]

For detailed traffic arrangement and mix laying procedures, refer to IRC:SP:55 and the above clauses in IRC SP 78.

IRC SP 78: Preparation of Premix (Clause 4.6) - Key Points & Specifications

• Mixing Equipment:

  • Use mechanical mixers for aggregate and bitumen blending.
  • Improvised drums allowed only for small-scale work.

• Heating of Bituminous Material:

  • Heat bitumen (except emulsions) in special binder tanks to avoid local overheating.
  • Maintain continuous supply at the correct application temperature.

• Aggregate Preparation:

  • Aggregates must be dry and warmed/heated before mixing.
  • Temperature at mixer entry should ensure proper coating and workability.

Typical Temperature Ranges (for reference)

Mixing Ratio (from Clause 3.3 - Proportioning)

• Follow mix design proportions based on gradation and bitumen content.
• Typical bitumen content: 4% to 6% by weight of total mix.
• Aggregate gradation as per MSS or CGPS specifications (close-graded).

flowchart LR
    A[Dry Aggregates] --> B[Heated Aggregates]
    C[Bitumen] --> D[Heated Bitumen Tank]
    B --> E[Mechanical Mixer]
    D --> E
    E --> F[Premix Output]

Summary: Proper premix preparation requires controlled heating of bitumen and aggregates, mechanical mixing for uniform coating, and adherence to mix proportions for durable surfacing.

Key Specifications & Formulas for Tack Coat Application (IRC SP 78)

1. Binder Types (Clause 3.4)

• Bitumen: VG-10 grade (IS:73), viscosity < 2 poise at application temperature.
• Emulsion: Cationic Bitumen Emulsion RS-1 (IS:8887/ASTM D2397).
• Cutback Bitumen RC-70: Only for <0℃ or emergency (IS:217).

2. Application Temperature

3. Rate of Application (Table 4)

4. Weather Restrictions (Clause 4.1)

• No application during rain or damp base.
• Atmospheric temperature > 10℃ in shade.

5. Summary Process

flowchart TD
    A[Prepare Surface] --> B[Heat Binder to Required Temp]
    B --> C[Spray Tack Coat Uniformly]
    C --> D[Allow Tack Coat to Set]
    D --> E[Lay Mix Seal Surfacing Immediately]

Note: Uniform application and correct temperature ensure proper bonding between layers.

Mixing Procedures - IRC SP 78 Key Points

1. Proportioning & Mixing (Clause 3.3)

• Dry mixing: Aggregate dry mixed for ~15 seconds.
• Binder addition: Hot bituminous binder added at specified rate (per para 3.3).
• Temperature: Binder and aggregates heated to temperatures per Table 5.
• Mixing duration: Continue until homogeneous coating on all aggregate particles.

2. Temperature Requirements (Table 5 - Typical Values)

(Exact values per Table 5 in IRC SP 78)

3. Preparation of Premix (Clause 4.6)

• Use mechanical mixers for uniformity.
• Bitumen heated in special tanks to avoid overheating.
• Aggregates must be dry and heated before mixing.
• Aggregate temperature at mixer entry must ensure proper coating and workability.

Summary Diagram: Mixing Process Flow

flowchart LR
    A[Dry Aggregate] -->|15 sec dry mix| B[Mechanical Mixer]
    C[Heated Bituminous Binder] -->|Added at specified rate & temp| B
    B -->|Mix till uniform coating| D[Homogeneous Premix]
    D --> E[Transport to site in insulated vehicles]

Note: Always refer to IRC SP 78 Table 5 for exact temperature ranges and para 3.3 for binder rates.

Spreading of Mix - IRC SP 78 Key Points

• Immediate Spreading: Mix must be spread immediately after mixing, preferably by mechanical pavers, spreaders, or graders (Clause 4.7).
• Surface Correction: Any unevenness should be corrected while the mix is still hot.
• Weather Restrictions: Do not lay mix in rainy weather, damp base, or when ambient temperature ≤ 10°C (Clause 4.1).
• Mix Thickness: 20 mm thick Mix Seal Surfacing on prepared granular/bituminous base (Clause 2.1).

Temperature Specifications for Mix Spreading (Table 5)

Rolling must finish before mat cools below rolling temperature.

Aggregate Grading for Mix Seal Surfacing (Table 3)

Rolling and Compaction - IRC SP 78 Key Points

Rolling Procedure (Clause 4.8)

• Use 8-10 tonne power roller.
• Start rolling at edges, move longitudinally towards centre.
• On super-elevation, roll from lower to upper edge parallel to carriageway centerline.
• Overlap each track uniformly until roller marks vanish and no further compaction/crushing occurs.
• Keep roller wheels damp to avoid mix picking.
• Correct high/low spots immediately while mix is hot.
• Cut edges at joints to full depth, paint with binder before placing fresh mix.

Temperature Specifications (Table 5)

Rolling must finish before mat cools below rolling temp.

Weather Limitations (Clause 4.1)

• No laying during rain or damp base.
• Ambient temperature > 10℃ in shade.

Surface Finish (Clause 4.10)

• Uniform, conforms to grade and cross-section.
• Max deviation: 6 mm under 3 m straight edge.

flowchart LR
    A[Mix laid] --> B[Start rolling at edges]
    B --> C[Roll longitudinally towards center]
    C --> D{Super elevation?}
    D -- Yes --> E[Roll from lower to upper edge]
    D -- No --> F[Continue rolling]
    E --> F
    F --> G[Overlap tracks uniformly]
   

Quality Control in IRC SP 78 (Clause 4.9)

• Quality control must follow IRC:SP:11 "Quality Control for the Construction of Roads and Runways".
• Ensure all construction phases comply with prescribed material and environmental conditions.

Key Specifications & Tables for Mix Seal Surfacing Quality Control

1. Weather Limitations (Clause 4.1)

• Do not lay mix seal during rain or if base/subgrade is damp.
• Ambient temperature must be above 10°C in shade.

2. Bitumen Selection (Tables 1, 2A & 2B)

Climatic Selection Example:

3. Aggregate Grading (Table 3)

4. Tack Coat Application Rates (Table 4)

IRC SP 78: Finished Surface Requirements

• Surface Uniformity: The compacted surface must be uniform and conform exactly to the grade lines and cross-sections shown in the plan.

• Straight Edge Test:

  • Use a 3 m straight edge placed on the finished surface.
  • Maximum allowable deviation under the straight edge: 6 mm.

• Aggregate Grading for Mix Seal Surfacing (MSS) / Close-Graded Premix Surfacing (CGPS):
  Refer to Table 3 for aggregate grading specifications (as per contract). Typical gradation limits ensure proper texture and durability.

Summary Table: Finished Surface Tolerance

flowchart LR
    A[Compacted Surface] --> B{Straight Edge Test}
    B -->|Deviation ≤ 6mm| C[Accept Surface]
    B -->|Deviation > 6mm| D[Rework Surface]
    C --> E[Conforms to Grade & Cross Section]

Ensure aggregates meet grading per Table 3 for MSS/CGPS to maintain surface quality and durability.

Opening the Road to Traffic (IRC SP 78 - Clause 4.11)

• Road Opening Timing: Open the road to traffic only after the bituminous mix cools down to ambient temperature to avoid deformation.
• Speed Restrictions: Impose initial speed restrictions to prevent mix displacement under fast-moving traffic.

Key Specifications and Tables Relevant to Traffic Opening

Important Notes for Traffic Management (Clause 4.3)

• Provide adequate traffic arrangements per IRC:SP:55 to ensure smooth construction without traffic interference.

Summary Diagram: Road Opening Process

flowchart TD
    A[Mix Placement] --> B{Cooling to Ambient Temp?}
    B -- No --> C[Wait]
    B -- Yes --> D[Open Road to Traffic]
    D --> E{Initial Speed Restrictions?}
    E -- Yes --> F[Impose Speed Limits]
    E -- No --> G[Normal Traffic]

In brief: Open the road only after cooling, control traffic speed initially, and ensure proper traffic arrangements per IRC:SP:55 to maintain construction safety and quality.